Oil-less air compressor

ABSTRACT

An oil-less air compressor mainly includes a motor, a crankcase, and a piston rod moving in the crankcase in rotary motion for external air to enter the crankcase via an air inlet thereof and be discharged from an air cylinder via an air outlet thereof into an external air tank. The air inlet of the crankcase is provided with a plurality of connecting bars to connect to a column centered in the air inlet, an annular filter element is mounted on the central column, and an end cap having a central hole is fitted in the center of the air inlet, so that external air could smoothly pass through the air inlet via through holes formed between the connecting bars.

FIELD OF THE INVENTION

The present invention relates to an oil-less air compressor, and more particularly to an air compressor that allows external air to smoothly enter an air cylinder and does not produce residual air pressure at a piston head thereof.

BACKGROUND OF THE INVENTION

FIGS. 1 and 2 shows a conventional oil-less air compressor, which includes a motor 11, an idler 12 and a bearing 13 transmitting kinetic energy produced by the motor 11 to a piston rod 14 for the latter to move in a crankcase 15 in rotary motion and a piston head 16 of the piston rod 14 to reciprocatingly move in an air cylinder 17, and a check valve 18 provided at an air outlet 21 of the air cylinder 17. When the piston head 16 is in a downward return stroke, external air is admitted into the crankcase 15 via an air inlet 19 thereof and enters into the air cylinder 17 via the piston head 16. And, when the piston head 16 is in an upward compress stroke, air in the air cylinder 17 is compressed to pass through the check valve 18 and discharged via the air outlet 21 into an externally connected air tank (not shown) for storage.

The air inlet 19 of the crankcase 15 is provided with a cover 2, which has a centered recess 20 for receiving an air filter 22 therein. The centered recess 20 is then closed using an end cap 23 having a central hole 231. Since the air filter 22 is directly positioned in the air inlet 19, and the central hole 231 on the end cap 23 is not in alignment with a direction in which external air passes through the air filter 22, the conventional air compressor does not allow air to smoothly enter thereinto. Moreover, the piston head 16 of the piston rod 14 is provided at a top with a long recess 161 having a through hole 160 formed therein, so that a check valve 162 is loosely screwed to the through hole 160 in the recess 161. When the piston head 16 is in a downward return stroke, air is admitted into the crankcase 15 and enters into the air cylinder 17 via the check valve 162; and when the piston head 16 is in an upward compress stroke, the check valve 162 bears against the recess 161 with a gap left between the check valve 162 and the recess 161 to produce residual air pressure thereat, forming an adverse influence on the smooth movement of air into and out of the air cylinder 17.

SUMMARY OF THE INVENTION

It is therefore a primary object of the present invention to provide an oil-less air compressor that has a plurality of connecting bars provided in the air inlet of the crankcase to extend between an inner edge of the air inlet and a column centered in the air inlet, an annular filter element mounted on the central column, and an end cap having a central through hole fitted in the air inlet, so that external air could be smoothly admitted into the crankcase and enter into an air cylinder via through holes formed between the connecting bars in the air inlet.

Another object of the present invention is to provide an oil-less air compressor that has a piston head provided at a top with a centered fixing hole and a plurality of through holes spaced around the fixing hole, and a disk-like check valve loosely screwed to the fixing hole of the piston head to keep the piston head in a completely plane surface. Whereby, when the piston head is in a downward return stroke, the check valve is in a floating and opened state to admit air into the air cylinder, and when the piston head is in an upward compress stroke, the completely plane surface of the piston head prevents forming of any residual air pressure thereat to adversely affect the smooth movement of air into and out of the air cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein

FIG. 1 is an exploded perspective view of a conventional air compressor;

FIG. 2 is an assembled sectional view of the conventional air compressor of FIG. 1;

FIG. 3 is an exploded perspective view of an oil-less air compressor according to the present invention;

FIG. 4 is an enlarged exploded perspective view of a piston rod for the oil-less air compressor of the present invention;

FIG. 5 is an assembled sectional view of the present invention; and

FIG. 6 is an enlarged exploded perspective view of a cover for a crankcase of the oil-less air compressor of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please refer to FIGS. 3, 4, and 5 at the same time. An oil-less air compressor according to the present invention mainly includes a motor 11, an idler 12, a bearing 13, and a piston rod 14. The piston rod 14 moves in a crankcase 15 in rotary motion, so that external air is admitted into the crankcase 15 via an air inlet 19 thereof when a piston head 16 of the piston rod 14 is in a downward return stroke. The air entered into the crankcase 15 then moves into an air cylinder 17 via the piston head 16. On the other hand, when the piston head 16 is in an upward compress stroke, air in the air cylinder 17 is compressed to pass through a check valve 18 and discharged via an air outlet 21 of the air cylinder 17 into an air tank (not shown) externally connected to the air compressor.

A cover 3 is provided at the air inlet 19 of the crankcase 15. Please refer to FIG. 6. The cover 3 has a round central opening 31. A plurality of connecting bars 32 are connected at an end to an inner edge of the round opening 31, and at an opposite end to a column 33 centered in the round opening 31, so that a plurality of through holes are formed by the connecting bars 32 between the round opening 31 and the central column 33. An annular filter element 34 is mounted at a central hole on the central column 33.

An end cap 4 having a central hole 41 and a plurality of retaining studs 42 spaced on an inner side of the end cap 4 is fitly closed to the round opening 31 on the cover 3 with the retaining studs 42 contacting with the inner edge of the round opening 31.

Please refer to FIG. 4. The piston head 16 of the piston rod 14 has a completely plane top surface with a fixing hole 163 provided at a center thereof and a plurality of through holes 164 spaced around the fixing hole 163. A check valve 165 in the form of a disc having a centered through hole 1651 is fixed to the plane top surface of the piston head 16 by downward extending a screw 166 through the through hole 1651 into the fixing hole 163, so that the check valve 165 is loosely screwed to the piston head 16 without leaving any recess or gap between the check valve 165 and the piston head 16.

With the above arrangements, when the piston head 16 is in the upward compress stroke, air in the air cylinder 17 is compressed, causing external air admitted into the crankcase 15 via the air inlet 19 and entered into the air cylinder 17 to be discharged via the air outlet 21 of the air cylinder 17. With the cover 3, the air inlet 19 allows external air to smoothly enter into the air cylinder 17. When the piston head 16 is in a downward return stroke, the check valve 165 is in a completely opened state to open the through holes 164 for air to smoothly pass therethrough into the air cylinder 17. Moreover, since there is not any recess or gap between the check valve 165 and the piston head 16 to produce any residual air pressure thereat, air is allowed to enter into and discharge from the air cylinder 17 smoothly.

In brief, the oil-less air compressor of the present invention is provided at the air inlet of the crankcase with a cover having the filter element mounted therein, and at the piston rod with the check valve that keeps the piston head in a completely plane surface, making the air compressor to take in and discharge air more smoothly. 

1. An oil-less air compressor, comprising a motor, a crankcase, and a piston rod moving in said crankcase in rotary motion for external air to enter said crankcase via an air inlet thereof and be discharged from an air cylinder via an air outlet thereof into an externally connected air tank for storage; said oil-less air compressor being characterized in that said air inlet of said crankcase is provided with a cover defining a centered round opening, in which a plurality of connecting bars are provided to connect at an end to an inner edge of said round opening, and at an opposite end to a column located at a center of said round opening, such that a plurality of through holes are formed in said air inlet by said connecting bars between said round opening and said central column; that an annular filter element is mounted at a central hole on said central column; and that an end cap having a central hole is fitted in said round opening of said cover by engaging a plurality of retaining studs spaced on an inner side of said end cap with the inner edge of said round opening.
 2. The oil-less air compressor as claimed in claim 1, wherein said piston rod has a piston head, on which a centered fixing hole and a plurality of through holes spaced around said fixing hole are provided; and wherein a check valve in the form of a round disc having a centered through hole is loosely screwed to said fixing hole on said piston head to keep said piston head in a completely plane surface; whereby when said piston head is in an upward compress stroke with said check valve tightly bearing against said piston head, no residual air pressure would form in said air cylinder at said piston head, allowing air to move into and discharge from said air cylinder more smoothly. 